Modern times. For generations, kids used to ask the same thing about bananas.
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Max♦Feb 17 '14 at 14:57

19

When you're highlighting text, the cursor changes to an I-beam on any decent UI.
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KazFeb 18 '14 at 6:46

7

I have seen straight cursor in some old DOS GUI apps and have also tried it in Windows and Linux - straight cursor just looks and feels nasty like handling a spoon straightly perpendicular to your face when eating (feeding yourself) or positioning your elbow to the center of your body when giving a handshake... Also can cause some Freudian associations when thought about :-)
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IvanFeb 19 '14 at 4:26

3

Also, consider that some text (for cultural reasons or others) are written vertically, having a straight mouse would hide the next letter after the one you point at. Making it go towards the right side and down makes it very practical in many situations.
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AkiFeb 20 '14 at 10:30

The historical reasons are given by some great answers here. However, I would like to add that a tilted pointer hides as less information as possible. Of course not in all cases, but generally, data is aligned vertically or horizontally. Therefore, the diagonally aligned cursor is not in the way.
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danijarMar 1 '14 at 1:45

When the XEROX PARC machine was built, the cursor changed into a tilted arrow. It was found that, given the low resolution of the screens in those days, drawing a straight line (left edge of arrow) and a line at a 45 degree angle (right edge of arrow) was easier to do and more recognizable than the straight cursor.

And of course Bill copied it from Steve who copied it from Douglas ;)
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Bart GijssensFeb 17 '14 at 13:38

6

@jjt the right edge of the arrow is 45˚.
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Jakob WeisblatFeb 17 '14 at 17:20

12

So pixel layout is the real reason :) To make it vertical and still look smooth the cursor would have to be twice as wide. Also that most def. is 45º, just think about the image... it's a grid.. one line goes down down down down, the other line goes down right down right down right. It must be 45º
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Albert RenshawFeb 17 '14 at 17:41

4

@AlbertRenshaw: ...at least if you assume square pixels--but that wasn't a given in those days (e.g., it wasn't normally true of an EGA or Hercules card at their maximum resolution).
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Jerry CoffinFeb 17 '14 at 20:55

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

Ok, that's your hypothesis. Can you give evidence that this is actually the reason, or even had any basis behind the 2D, small, on-screen arrow? Surely if this was the case then it wouldn't be an arrow at all, it'd be a finger?
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JonW♦Feb 17 '14 at 18:58

I actually like this answer the best. I understand the technical answers and I viewed Doug Engelbart's demo where the pointer is indeed vertical. However, this mimics the hand better, looks more natural -- and in addition, it does not obscure the pixels right below the target, which the user is presumably more likely to want to see than pixels to the southeast of the target, when viewing it, due to the heuristic that many graphics employ horizontal and vertical guides. Also, why does it have to cite sources, when it has a picture of a hand?
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Gregory MagarshakFeb 17 '14 at 21:24

The reason the arrow was tilted to the left was so that the click position was easier to calculate, because the origin of the cursor's bitmap was in the upper left. This saved the mouse tracking subroutine a calculation on every click (its not much but it helped on older machines).

@PatomaS: That was a later generalization when machines became fast enough.
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MSaltersFeb 17 '14 at 15:13

62

While this certainly sounds plausible, your source is just a Reddit post that has no citations in it, so could just be totally made-up.
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JonW♦Feb 17 '14 at 15:33

11

Although this is a theoretical benefit, I highly doubt it seriously informed the decision. Even by the standards of the 1970s, adding two offset numbers is an extremely trivial operation that could easily fit within the mouse update interval. Remember, just like today, there were other pointers in use depending on the application (e.g. text selection, row selection, paintbrush) and they didn't all have (0, 0) origins but worked just fine nonetheless.
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nmcleanFeb 17 '14 at 17:05

With regard to the calculation time, my ballpark estimate is that it the custom hotspot took between 4 and 8 instructions at 400,000 instructions per second, or between 1/50,000 and 1/100,000 second for each mouse update: news.ycombinator.com/item?id=7253841
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Michael GearyFeb 17 '14 at 21:35

Low level visual cognition

In addition to the various answers given, there is also sense in a tilted mouse pointer if one considers the visual processes in our brain.

Visual information arriving from our eyes is first processed in the primary visual cortex by the V1 area, then by the V2 area. These two areas recognise low-level visual features (hue, lightness, size, orientation, etc.).

The popout effect

As visual information is processed by these areas, some visual irregularities truly pop out (ie, they are highly distinguishable), which greatly helps visual search (trying to find an item in a visually busy field). The popular name for this phenomenon is the popout effect.

Orientation

One such irregularity is orientation, and it is neatly explained by the following illustration:

You should find it next to impossible to find the search target in 1 (a straight line in a group of straight lines). But rather easy in 2 - finding a tilted line in a group of straight lines. In 3 it should be equally next to impossible to find the tilted line in a group of tilted lines (of the same angle).

Since vertical and horizontal orientations are the most common ones on screens (and in life in general) a tilted mouse pointer will be more easily found.

I have a feeling that this answer is totally unrelated to the real reason for the tilt, but it is cool nonetheless. However, whenever I need to find my mouse, I just wave it about wildly until I see it moving.
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naught101Feb 20 '14 at 1:23

2

@naught101: I do that too. We should have animated (spinning?) mouse pointers so they really stand out and we don't need to wave the mouse about to see where the pointer is :-)
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BrendanFeb 20 '14 at 8:30

2

MIT Lisp Machines had a cool feature to help find the mouse cursor: if you moved the mouse back and forth quickly, the cursor would magnify (the documentation described it as "big like Godzilla").
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BarmarFeb 20 '14 at 23:45

2

@cr0ybot you can already do something like that in Windows. I had a synaptics driver and it had an option to show circles around pointer when certain key was pressed. I don't have that PC right now but may be googling might help.
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user13107Feb 21 '14 at 3:19

5

@user13107 I'm sure that's actually a standard feature. Control Panel|Mouse|Pointer Options|Show location of pointer when I press the CTRL key. Another option that helps find the mouse (though imho it's less effective and more annoying than the former): Display pointer trails.
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Craig YoungFeb 21 '14 at 8:36

I've always thought that the arrow cursor is shaped similarly to your hand if you were point (naturally) at the screen with your (as typically dominant) right hand.

I have no support of this other than my own subjective experience but it strikes me as a natural shape when trying to relate real world interaction into a low resolution computer screen where rendering something resembling a hand would be impossible.

[Edit: Someone stole the only thunder I've ever had on StackAnything. Thanks!]

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

1

I think this is an actual "non-historical" answer. Otherwise we would've seen reverse-angle and straight cursors in abundance.
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DenFeb 17 '14 at 17:17

2

@Den We have not seen user interface operating systems themselves in abundance. Most of the world is based on several operating system hegemonies.
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KazFeb 18 '14 at 6:44

2

@Kaz - most of games have custom cursors. Old Dungeon Keeper is a perfect example - it's literally a hand shaped cursor pointing the way your hand would - inclined to the left. I am sorry but this answer is the only correct one.
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DenFeb 18 '14 at 11:46

5

It's curious how this answer got 2 upvotes but a same answer with an image got 122.
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jinaweeFeb 20 '14 at 15:12

1

@jinawee: Because people like pictures and don't read words as much. And the one with the hand has an arrogant 'there, I proved it' attitude - despite neither that one or this one being based on any actual evidence, just reverse-engineered guesswork.
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JonW♦Feb 20 '14 at 17:06

An arrow with edges that are vertical and horizontal, or that are +/- 45 degrees, would also clearly identify a point without aliasing issues, but would obscure more of the screen underneath. Having one edge vertical and one 45 degrees reduces the obscured width.
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supercatFeb 17 '14 at 20:15

1

@supercat - Yes. And also, such arrow will have angle of 90 degrees and will look too "pointless" and as a result ugly. 90 degrees arrows are OK for some tasks, but not for mouse pointers (IMO).
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johnfoundFeb 17 '14 at 21:23

1

Drawing a sharp anything is difficult with antialiasing. If you want sharp, you game the aliasing. :)
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KazFeb 18 '14 at 6:43

@Arne - It must be 22.5 in order to be OK. But is usually drawn as 2px:1px ratio. That is why it looks a little bit wrong angled.
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johnfoundFeb 23 '14 at 22:39

The angle, the cursor is inclined at gives a better feeling of pointing something. A cursor straight at 90 degree would not provide a good effect.It provides improved appearance on low resolution screens.

Also the position calculation would become a lot easier when done from the top left corner of the pixel.